Method and apparatus for graveling wells



May 16, 1944. l.. c. UREN METHOD AND APPARATUS FOR GRAVELING WELLS Filed March 27, 1942l no2. l

INVENTOR ATTORNEY Patented May 1e, 1944 UNITED STATES PATENT OFFICE,

Lester Charles Uren, Berkeley, Calif., assigner to The Texas Company. New York, N. Y., a oorporation of Delaware Application Mar-cn e1, 1942, serial No. 436,424 I 7 lClaims. (Cl. 166-1) This invention relates to the completion of wells and more particularly to a method and an apparatus by means of which a uniform pack of gravel or other granular material can be placed in a well bore around a perforated liner or screen.

The principal object of the invention is to proand Water from unconsolidated and semi-consolidated formations, it is usual to provide a perforated liner or screen through the .producing sand.

oi' the oil, gas or water that it is desired to produce through the gravel envelope. It is important that the gravel particles be of suitable size, so that when placed in the well cavity. the openings between particles will be of such size as will restrain influx of detrital material from Athe prod-ucing formation. Also, the method of placement oi.' the gravel in-the well cavity should be such that the gravel particles will be thoroughly compacted to form an envelope of minimum porosity and maximum density.l Imperfect placement of gravel inthe well cavity will often result in an envelope of irregular permeability, Der- This is designed to prevent the walls of the well l unduly restricted. To avoid this, it has become common practice to ream the well to largerthan-normal diameter through the producing interval, forming an annular cavity about theliner, and then to illl this cavity with coarse sand or gravel. Fluids move freely through the interstices between the gravel particles, .but loose detrital materialbridges the openings through which the fluids `move, so'that little or no formational sand 'or shale particles may reach the liner. Furthermore, due to the larger diameter of the well through the producing interval. the nuids enter the well cavity with lower velocity than would be the case in a well of smaller diameter, and have less carrying capacity for detrital material.

f Processes for placing vgravel outside-of screen pipe in well cavities generally involve circulating the gravel 4into place through a column of tilpllgfo' hbetween two concentric columns of velope to passage of fluids.4 When clay-laden'water is used asa placementmedium, the clay often tends to geland accumulate between the gravel particles, thereby restricting subsequent passage tubing, using clay-laden fluid, water or oil as a haps leaving open channels through which detrital material from the producing formation may readily pass. Present commonly used methods of circulating gravel into wells sometimes result in for-mation of gravel envelopes of highly irregular permeability that can be only partially effective in serving their intended purpose.

In accordance with this invention, the novel feature resides in the development of conditions within the well cavity, whereby the gravel particles are caused to settle downward through an y ascending stream of uid that frees them oi occluded detrital material and adherent clay, these foreign materials being circulated to the surface in suspension in the ascending fluid. Two streams of.- iluid'ar'e employed, one to carry the gravel down to the well cavity from the surface. the other being simultaneously ejected horizontally outward through the liner perforations into the well cavity, at or immediately above the level of the surface on which the descending particles of gravel are accumulating. This latter stream of iluid is maintained in such volume that its ascending velocity in the'well cavity will permit gravel particles to settle, but finer and lighter particles of detrital material'will be sweptupward toward the surface. The two streams merge at the level of injection of. gravel particles into the well cavity and rise together to the surface at a velocity that permits no 'further settling oitV the effectiveness o'. the gravel envelope. For a better understanding of the invention reference may be had ing in' which:

to the accompanying draw-` Figure l is a sectional elevation through va well bore and surface equipment, showing gravel -being deposited in the well cavity, and

Figure 2 is an enlarged sectional elevation of the lower` end of the gravel placing tubing:

Referring to the drawing, a well bore I0 is shown as having been drilled through several formations including an oil bearing sand I2. A casing I4 is placed in that portion of the hole above the producing formation and is cemented in place in the usual manner, 'as at I8. That portion of the hole within the producing formation I2 is preferably underreamed by mechanical d r hydraulic means to form the well cavity I8. The rst operation in equipping the well i'or gravel packing by the method and means herein proposed consists in lowering a perforated liner or screen 20 of such construction that it presents a smooth exterior and interior cylindrical surface. The liner 28 may be lowered in any-lultable manner, such as on the lower end of a string of tubing, not shown, suitably connected to-the upper end of the liner. as by a coupling having a left-hand thread. 4A packer 22 on the lower end of the liner 2l may be set against the wall oi' the well justbelow the'cavity I8 to hold the liner firmly at this pointso that it will not tum or be lifted out of its position by subsequent manipulation of the circulating equipment. After the packer setting operation, the' tubing used for lowering the liner may be turned in a clockwise direction, thus disengaging the left-hand thread-` ed connection so that the liner will be left in the well while the tubing string is withdrawn.

A column of pipe, such as light casing 24, of somewhat larger diameter than the liner 28 is lowered into the well as'by means of the pulley and cable 28. The lower end of the column 24 `is equipped with a foot-piece 28 closing theanquent'placement of gravel in the well cavity. Eventually, the disc 40 is again withdrawn to the surface with the tubing 22 and the packers 34 thereon.

The annular space between the well casing I4 and the light casing string 24 is closed at the surface by a casing. head 42 which isl equipped with a gland 44 that permits of vertical movement of the casing string 24. The latter string is of smooth exterior construction near its upper end to permit of this vertical movement through the gland 44. A side outlet 46 connects the annular space between the casings I4 and 24 to a storage tank 48. The annular space between the casing string 24 and the tubing 82 is closed by a head 50 which is attached rigidly to both strings so that'they may be raised and lowered together. A side connection l2 through the head lil permits of forcing gravel suspended in a liquid circulating medium under pump pressure into the annular space between the casing string 24 and the tubing 22, the circulating medium and suspended gravel passing down through this annular space, through the annular space between casing 24 and liner 2|.'and thence out to the well cavity I8 through the ports 88 in the foot-piece 28. As is shown more clearly in Figure 2, the tubing 82 extends to a somewhat greater depth than `the casing string 24 and its foot-piece 28 so that fluid circulating down through tubing 82 and outward through ports 28 and the perforations in the liner 2l will enter thewellcavity I8 below the gravel carrying fluid ietted from the ports 20 and the foot-piece 28.

At the surface the storage tank 48 provides storage for the circulating fluid to be employed in graveling the well. A pump 54 draws fluid from the tank 48 through\the valved pipe 58 and .forces this fluid through a flexible connection Il and then through the: pipe 82 into the annular space within the casing string 24. The fluid then passes through this annular space downwardly and into the well cavity I8 through the ports Il in the foot-piece 28. Connecting with the pump discharge line through asuitable 'control valve Il is a gravel container 42 adapted to'feed gravel into the fluid from the pump-84 before the fluid enters the upper end of the string 24. The con- 28 will thus telescope over the liner 2l so that the two tubes will be concentric, leaving an annular space between.

Another column of tubing 82 of such size that it may pass inside of the liner 20 is then lowered from the surface, this column of tubing .being equipped near itslower end with two packers 34 separated a short distance and of such size that they fit snugly against the internal surface of the liner 28 and yetslide freelythereon. .The bottom of the tubing 32 is closed, as at 26, and is provided with openingsA I8 between the packers 24 to permit of uid forcedl down through the tubing 22 iiowing horizontally outward through the annular space between. the liner I20 andthe tubing 22 and thence through the liner perforations into the well cavity I8. Mounted on the tubing I2 above the uppermost of the two pack- .ers 84 is a metal disc 4l, centrally bored Kto slip easily over the smooth exterior suriace of the tubing 22' and of a diameter slightly larger than the liner 20. As the lower part'of the tubing 22 with the packers passes down inside the liner 2t, the disc 40 comes to rest on top ofthe liner 20, thus closing the annular space between the liner 28 and the tubing 22 and remains there tainer 62 may. of course, be maintained under pressure. and, ii! desired, two of these containers may be used so that one may be discharging while the other is being iilled with gravel. Another connection I4 from the discharge line from the pump I4 leads through a ilexible connection 88 to the top of the tubing column 32. By means of the valvesll and 18 in the discharge lines from the pump 54, the volume of iiuid entering the ltu-bing 32 and the casing string 24 can be regulated. It'is understood that suspension and hoisting mechanism, indicated only by the pulley 28, will be provided above the well head to manipulate the casing liner and tubing strings inthe well and to raise the tubing 82 and the casing string 24 simultaneously as the graveling operations pro- In the application of the invention. the well cavity n is mst reamed through the reservoir rock I2 by; means ofl mechanicalv wall scrapers or under-reamers, or by hydraulic force as shown in my earlier U. S. Letters Patent No. 1.530.221, granted March 17, 1925. The perforated liner or screen 28 is then placed in the well. supported on the packer 22 and extending upwardas the tubing u as manipulated during subsel 1y through the wen cavity und c snort dumm assaoea up into the well casing above. The tubing on which the liner lis lowered is disengaged and removed, as previously explained. The special well equipment for controlling the movement of circulating streams of fluid is then inserted in working position i the well and the surface facilities assembled and connected.v Gravel is placed inthe container 62, and a sufficient quantity of the circulating fluid to be used is placed in the storage tank 48. This fluid may be crude petroleum from the well, water or clay-laden water. For purposes of the present description, it is assumed that crude petroleum will be the uid used. Casing 'string 24 and the tubing string l2 are loweredv until the foot-piece 28 and packer assembly 34 are near the bottom of the well cavity, the packer being slightly below v the level of gravel discharge,'as indicated in Figure 1.

The pump-54 is started, drawing oil from the tank 48, forcing it through the head iii and down through the annular space between strings 24 'and I2. and v24 and the liner 20, and thence through the ports 30 into the well cavity I8. Circulation is continued until the well is filled with oil and overflows at the surface from the annular space between the pipe string 24 and the casing I4, through the outlet 4t and into the tank 48. -Duringthis time. valve will be open and valves Iii and 68 closed. The valve Il is then opened, admittingoil under pump pressure to the top of the tubing column 32. causing oil to flow down through that column out through the ports 24 between the packers and into vthe wellcavity through those perforatlons in the liner 20 between the packers 34. With both streams of circulating fluid thus established, the valve 60 controlling the flow of gravel into the descending stream of oil in casing string 24 isv opened slightly so that the gravel particles will ow down the annular space between tubing string. 32 and the casing string 24 to be discharged' into the well cavity i4 through .the ports 30 in the foot-piece 28. The flow velocities of the two streams of aswashed free of adherent clay and occluded .de- .trital material, these impurities being swept upward toward the surface by the ascending fluids. The two streamsof fluid merge in the well cavity at the level of the discharge ports in footpiece @t and rise as one stream through the ular space between casings iii and 24. discharging with the entralned detrital material inta` storage tank d3.

Slowly, as gravel is deposited in the well cav.- ity, casing 2d and tubing 32 are simultaneously raised, maintaining their relative positions unchged. Flow continues, depositing washed gravel in the well cavity until it is filled and tubes it and 32 have been withdrawn up into the casing above.. curiose connections are broken. and tubes '32 and it are Ywithdrawn from the well in the order .As the upper packer 84 near the lower Circulation is then stopped.

liner 2l.. it engages loose disc4ii which thus is removed with the tubing to the surface, leaving the upper endl of the linear 20 open to receive the production tubing when the well is later equipped for production.

After the casing column 24 Vhas been removed from the well, a short joint of casing, not shown, preferably of the same size as the liner 2li and carrying. a wall packer of any suitable type. is lowered and the upper end of the liner, then embedded in the gravel envelope is engaged. 'I'he packer is then set against the inner wallof the well casing I4, thus closing the annular space between the liner 20 and the casing i4 and permanently conning the gravel within the well cavity I8 and the extreme lower end of the well casing I4. After the packer has been set, the tubing used to lower the short casing section is disengaged and withdrawn to the surface. The samey purpose may also be served, but perhaps not quite as effectively, by placing a packer on velocity in the well cavity will permit the gravel particles to settle rapidly in the ascending stream. The larger and heavier the gravel particles and thelower the density of: the circulating l fluid, the more readily will the gravel settle and cles ofv crushed barite, hematite, siderite, g'alena or other heavy minerals of density ranging considerably above that of ordinary siliceous rocks 'of which most gravel particles are composed.

The two streams of fluid -entering the well cavity at different depths create three zones of classification for segregation of the suspended fluids. In each of these three zones the ascending fluids will have a different ascending ve- 10cm. The volume-or fluid entering the cavity through the liner perforations will normally through this zone of low ascending velocity fluid,

i. e.. the zone of low ascending velocity" or washing and gravel deposition. Here the descending gravel particles are washed free of ady herent clay and other low-density contaminants,

and gravitational forces deposit the gravelparticles in much the same fashion that sedimentation occurs in nature.

After the two streams of fluid merge in the well cavity above the foot-piece ports 30, a much greater ascending velocity is created due to the greater volume of liiuid\in motion. 'This is the (usually less than that of silica, 2.6) may settle through the ascending fluid. Heavy or relatively coarse gravel particles, however, may settie in t4 zone. Once the ascending uids have entered the annular space between casings il and 24 above the well cavity, the upward velocity of the fluids is further increased because of the reducedilow cross-section, and all solids in suspension in the fluid, whether detrltal material or gravel, are swept rapidly toward the surface. Thls is the "zone of highest ascending velocity" or of expulsion. Figure 1 shows these zones of differing ascending velocity. e

The effect' of the ascending stream of fluid in the well cavity may be compared with that of the hydraulic classifier used in ore-dressing operations. For a iluid of given specific gravity and ascending velocity, there is a certain optimum size of solid particle that may be lifted by the ascending stream; or, for solid particles of the same size but variable density, there is a certain minimum density of material that may settle through the ascending stream. Increasing the ascending velocity of the fluid will lift coarser solid particles and particles of higher density, and vice versa. l-tittingerl Richards and others have proposed mathematical formulae expressing these relationships.

It is believed that the method of gravel placeinent herein described accomplishes .formation of a gravel envelope illter about a well liner that is superior to one produced by any' otherY process now in use. With condtions in the well cavity properly controlled, a gravel envelope of maximum and uniform density is secured because the gravel particles are settled upon each other through moving fluid, with opportunity f for orientation and adjustment of particles in accordance with their size and form. This is natures process of sedimentation. vAt the same time, the gravel particles are washed free of clay or other detrital material that would tend locally to reduce thepermeability of the gravel envelope. No such material may be deposited with the gravel in the well cavity. 'I'he liner perforations are likewise washed free of all detrital material that might later tend to obstruct them. The flow of fluid isfirst outward toward the wall of the well cavity before it assumes its upward course. Hence, gravel particles in each successive layer are propelled tothe perimeter of the well cavity. filling yall remote and irregularly shaped recesses-if there be such-before the gravel is deposited about the liner perforations. Upward circulation of fluid along the walls of the well bodied in the following claims. Diuerent circulating fluids may be used: oil. water, or a suspension of clay in water, for example; and one iluid may be used as a gravel carrying medium and another as a washing' medium. Where gravel is mentioned, any granular material insoluble in the circulating fluids may be. substiarrangements of tubing heads, packers, etc. are

possible, and for some conditions some other arrangement than that described herein may be preferable.

Iclaim:

1. A method of placing granular material in s well cavity which comprises circulating a quartity of the granular material in a carrier iiuid downwardly through a string of tubing and outwardly in a lateral direction into the cavity. simultaneously circulating a' stream of liquid downwardly to the cavity through a second string of tubing, electing said liquid laterally into the cavity at a point below the entrance of the granular material and carrier uuid, so that the liquid will pick up detrital and foreign material and carry it upwardly to the surface with said carrier nuid through another string oi.' tubing, the granular material-settling into the cav-A ity through said liquid, and maintaining the levels of ejection of the granular material and said liquid into the cavity slightly above the level` cavity carries all detrital material caving fromthe walls upward .toward the surface'so that it may never enter the zone of gravel deposition.

If clay-ladenwater is used as a gravel-'place- A ment medium, the -fluid issuing'through the liner ,producedf Use a of crushed vparticles of some heavy mineral frather than4 ordinary siliceous sol material, ofgwhich stream vgravel is ordinarily compemwill give further assurance of a clean. `dense and highly permeable filter bed about the well liner.

In the foregoing specifications I have described the preferred arrangement of equipment and method of conducting the gravel packing opera- "mL j tion. This, however, is merely by way of ex ample, and it should be understood that other arrangements of equipment and other methods of conducting the operation are possible without of the deposited granular material while the cavity is being filled with the granular material.

2. A method of placing granular material in a weli cavity which comprises circulating a quantity of the granular'material in a carrier fluid into the cavity through a string of tubing so that the granular material will settlein the eavity, simultaneously circulating a stream of liquid 'downwardly to the' cavity through a second string of tubing, ejecting said liquid into the cavity at a point slightly below theentrance of the granular material and carrleriluid and directly' above thetop-of' the deposited granular material; so that the liquid will pick up detrital and foreignA material and carry it upwardly to thev surface with said carrier fluid'throuh another string of tubing, and gradually raising said first and second string of tubing as the ydeposit of granular material is built up in the cavity.

3. A method of placing granular material in a well cavity which .comprises circulating a quan, tity of the granular material in a carrier fluid into the cavity through a string of tubing. simultanecusly circulating a stream of liquiddownwardly to the cavity through a'second string ottu'bing, electing said liquid into the cavity st a point lust lbelow the entranceiof the granular material and carrier iluid. to create a sone of washing and Agravel deposition from which detrital and foreign matter is carried upwardly' through a sorting zone of higher ascending velocity within the cavity and then to the surface through an expulsion sone of still higher ascending velocity above the cavity,` and maintaining the: levels of ejection of the granular material and said liquid into the cavity slightly above the level ofthe deposited granuai ma while the departing from the fundamental concepts em- 7s cavity is being filled with the granular material,

4. In an apparatus -for placing gravel in the lproducing zone of a well, aperforated liner extending vertically through4 said zone, a string of tubing extending downwardly through the well,

the lower end ofisaid tubing surrounding and having sliding engagement with the outer surface of said liner and provided at its lower end with at least onelateral discharge opening, a

second string of tubing extending downwardly 5 through said cavity, a string of tubing extending downwardly throughthe weil, a foot-piece onl the lower end of said tubing surrounding and having sliding engagement with the outer surface of said liner and provided with a plurality of radial. discharge openings, a second string of tubing closed from the surface, the lower portion of said second tubing string extending within said liner and provided with a lateral opening adapted to dis! charge outwardly through the liner perforations at a point below the discharge y'opening oi the first-mentioned tubing string-means for forcing a mixture of granular material and a carrier uid downwardly through said firsttubing string .and

means for forcing a stream-of liquid downwardly through said second tubing string. 5. In an apparatus -for graveling alwell provided with a casing and an enlarged cavity in a producing formation, a perforated liner extending vertically through 'said cavity, a string of tubing extending downwardly within said casing with the lower end 'of the tubing surrounding and said packers adapted to discharge outwardly through the liner perforations at a point below 'the discharge openings of said foot-piece, means tubing string and outwardly into said cavity .4 'through the openings in said footpiece, and means for forcing a stream of washing liquid v downwardly through vsaid second tubing string l fork forcing a mixture of granular material and a carrier fluid downwardly through said first `and outwardly through the opening between the having sliding engagement with the outer surl face of said liner and provided at its lower end with a leastv one lateral discharge opening, a sec'- ond string of tubing extending downwardly 'from the surface with the lower end of said second 1v tubing string extending within said liner and having sliding engagement with the inner surface of the liner and provided with a lateral opening adapted to discharge outwardly through the liner perforations at a point below the discharge opening of the first-mentioned vtubing string,

means for forcing a mixture of granular material and a carrier iiuid downwardly through said first tubing string and means for forcing a stream of washing liquid downward through said second tubing string, the arrangement being such that the washing liquid will-pass outwardly and upwardly through the descending granular material so as to -pick up the lighter, foreign matter from the granular material and' carry it upwardly to the surfacethrough the-space between the casing and the first-mentioned string oi tubing. 6. In an apparatus for graveling a. well pro- .vided with an enlarged cavity in .a producing formation, a perforated liner extending vertically` packers and through the liner perforations into the cavity.

7. In an apparatus for placing gravelin a well -provided with an enlarged cavity in a producing formation, a perforated liner lextending vertically through said cavity, a string of tubing extending downwardly through the well with the lower end of the tubing surrounding and having sliding engagement withA the outer surface of said liner andprovided at its lower end with at least one discharge opening, a second string of tubing extending downwardly through the well within said first tubing string, the lowerv portion of said second tubing string extending within said liner andprovided with an; opening adapted to discharge outwardly through the liner perforations at a point below the discharge opening of the first-mentioned tubing string, an annular cover Amember slidably disposed around said second tubing string and adapted to engageand cover the upper end of said liner when the lower pori tion of the second tubing string is Within the liner, means for forcing a mixture of granular material and a carrier fluid downwardly through `said first tubing' lstring and means for forcing a stream of washing liquid ldownwardly through said second tubing string.

, vLESTER CHARLES UREN.` 

